What is this thing?
This is a highly efficient, yet very compact mob farm, built in the skies high above my base.

How does it work?
When a mob - a Creeper, Skeleton or Zombie - spawns, it immediately hits a tripwire which triggers a row of pistons that pushes the mob into a water channel. This channel leads to the main channel and sends the mob to an adjustable fall of 23/24 blocks. Any item that the mob drops goes through a hopper into a double chest.

To go with the trap itself I made a snowball-shaped control room which has some simple, yet useful functions:

- Adjustable fall height, which means the trap can either be used as an XP farm without AFKing (due to the limit on natural mob spawns) or as an automatic farm with AFKing
- Special drop farming option, all it does is open the bottom part of the killing chamber, which allows to safely kill mobs with a special item (mobs with a special item survive the fall)
- Lava blade to automatically kill any mobs left in the killing chamber
- Creeper killer, which shoots an instant damage splash potion (rarely a creeper may survive the fall, and I guess you don't want things to get messy when you want to farm those special items...)
- Can indirectly be used as a record farm as well

The buildTo make a long story short... yes, it took a while. The Minecart system leading to it and the control room went relatively fast, but the spawning room unsurprisingly took a long time, or more specifically the first layer of it.

I wanted to make it out of snow right away simply because it's nice and white so it kinda blends it with the sky, but it was only until the final moment when I came up with the snowball thing, which actually works quite well and looks decent.

the farm has 512 spawning spaces: 128 per column, 64 per row, 16 per chamber. It produces about 4000 items per hour - that is 7.8 items per spawning space. As a comparison, the mob trap on my old survival world which uses a flusher system and has 432 spawning spaces 'only' produces about 2000 items per hour, or 4.6 items per spawning space.

- Got rid of the wonky brewing stand table thingys- Added more detail- Added more storage- Made the lightning nicer- Updated images - video is a little outdated but the main stuff didn't change

Update #4 : 05/29/2013 7:09:18 am5/29/13

Update 29.5.13:Added a video!

Update #3 : 04/28/2013 3:28:28 pm4/28/13

Update 28.4.13:Some much needed changes.

- Redid all the wiring of the control room- Added a special drop farming option for... safer farming of special drops (armor, swords, etc.)- Added a lava blade- Redid the creeper killer- Removed the piston that closes the killing chamber- Removed the button that moved the block on top of the hopper when farming XP- A bit of cleaning up the place- New pics- Updated world download- Changed description

Update #2 : 04/13/2013 2:16:14 pm4/13/13

Update 13.4.13: Added a world download of the design world, which contains roughly the same trap except smaller.

Update #1 : 04/06/2013 3:48:10 pm4/06/13

Update 6.4.13: Doubled the size, from 256 spawning spaces to 512. This has doubled, if not tripled spawning rates! Now getting about 4000 items/hr, whereas before it was about 2000.

I might eventually double it's size again and bring it up to 1024 spawning spaces, it just takes a LOT of time - and 9 stacks of iron, not mentioning 5 chests of snow blocks... oh yeah, also new images and description.